Kindly listen to the advice posted by others before claiming resolution.
substr_count() returns the number of times the needle substring occurs in the haystack string. Please note that needle is case sensitive.
Your original question was quite clear in stating you wanted a case insensitive comparison, you even put that in upper case to emphasize.
stripos(), available in PHP5, is case insensitive, strpos is not. Also, just so you know, the function you used doesn't count overlapped substrings and stripos is also binary safe, which can be handy in some situations.
Sorry, but had to post this, no disrespect intended.